The present invention relates generally to printing devices, and in particular, to printing devices that employ a full width array print bar.
An ink jet printer of the type frequently referred to as drop-on-demand, has at least one print head from which droplets of ink are directed towards a recording medium. Within the printhead, the ink is contained in a plurality of channels. Piezoelectric devices or power pulses cause the droplets of ink to be expelled as required, from orifices or nozzles located at the end of the channels. In thermal ink jet printing, the power pulses are usually produced by resistors, also known as heaters, each located in a respective one of the channels.
The heaters are individually addressable to heat and vaporize the ink in the channels. As a voltage is applied across a selected heater, a vapor bubble grows in that particular channel and ink bulges from the channel nozzle. At that stage the bubble begins to collapse. The ink within the channel then retracts and separates from the bulging ink thereby forming a droplet moving in a direction away from the channel nozzle and towards the recording medium whereupon hitting the recording medium a spot is formed. The channel is then refilled by capillary action which, in turn, draws ink from a supply container of liquid ink. Operation of a thermal ink jet printer is described in, for example, U.S. Pat. No. 4,849,774.
The ink jet printhead can be incorporated into a carriage type printer or a page width type printer. A carriage type printer typically has a relatively small printhead containing the ink channels and nozzles. The printhead is usually sealingly attached to a disposable ink supply cartridge and the combined printhead and cartridge assembly is attached to a carriage which is reciprocated to print one swath of information (equal to the length of a column of nozzles on the printhead) at a time on a stationary recording medium, such as paper or a transparent recording medium. After the swath is printed, the paper is stepped a distance equal to the height of the printed swath or a portion thereof, so that the next printed swath overlaps or abuts therewith. The procedure is repeated until an entire page is printed.
By contrast, the page width printer includes a stationary printbar having a length equal to or greater than the width of the recording medium. The recording medium is continually moved past the page width printbar in a direction substantially normal to the printbar length and at a constant or varying speed during the printing process. Because the printbars have an arrangement of substantially linearly aligned nozzles, the alignment of the printbar with respect to the recording medium is critical.
Printers typically print information received from an image output device such as a general purpose computer. Typically, these output devices generate pages of information in which each page is in the form of a page description language. An electronic subsystem (ESS) in the printer transforms the page description language into a raster scan image which is then transmitted to a peripheral or image output terminal (IOT). The raster scan image includes a series of scan lines in which each scan line contains information sufficient to print a single line of information across a page in a linear fashion. In the page description language, generated pages also include information arranged in scan lines.
In printbars which print a single line of pixels in a burst of several banks of nozzles, each bank printing a segment of a line, the banks of nozzles are typically fired sequentially and the nozzles within a bank are fired simultaneously. An ink jet printbar having banks of nozzles is described in U.S. Pat. No. 5,300,968, which is incorporated herein by reference. These printbars include a plurality of printhead dies, wherein each die prints a portion of a line. Within the die, the banks of nozzles print a segment of the portion of the line.
It will be appreciated that the continuous movement of the recording medium in the process direction would require all of the nozzles to be able to fire simultaneously to assure that the printing of all portions of the line of pixels is collinear. Simultaneous firing of all of the nozzles of page width printbar, however, is impracticable. In particular, such a firing would require too much energy and would generate too much heat. As a result, as a practical matter, the nozzles must be fired sequentially. Because the nozzles fire sequentially, the continuous movement of the recording medium raises an issue with regard to the linear alignment of the printing.
To address this issue, U.S. Pat. No. 5,619,622 teaches, among other things, a full width array printing device that employs an angled printbar. The angled printbar allows sequentially fired nozzles to achieve collinear printing when the recording medium is continuously moving. Because of the angled printbar, each printhead die starts on a new print or scan line. Accordingly, each die prints data corresponding to a different raster line. Because each print die prints on a different raster line, U.S. Pat. No. 5,619,622 teaches a raster interface or wedge buffer that converts full-width raster data to mini-rasters for each print die.
While the solution taught by U.S. Pat. No. 5,619,622 adequately achieves collinear and rapid printing for use with a continuously moving recording medium, that solution requires additional cost associated with the raster data reconfiguration step. Such cost arises from the inclusion of the wedge buffer.
A need exists, therefore, for a page width printer controller that is operable to achieve collinear page width printing for use with a continuously moving recording medium that avoids at least some of the cost associated with reconfiguration of the raster data as described above.
The present invention fulfills the above needs, as well as others, by providing a method and arrangement for printing data arranged as a plurality of scan lines using a printbar circuit that includes an output buffer and a serial data buffer; the serial data buffer connected to receive the scan line data serially without reconfiguration. The output buffer is connected to receive the scan line data from the serial data buffer. The printbar circuit causes printing in accordance with the scan line data stored in the output buffer. Thus, the scan line data is received into the serial data buffer in scan line format, thereby eliminating the need to reformat the data.
A first embodiment of the present invention is an arrangement for printing a raster image organized into a plurality of scan lines on a recording medium, the arrangement including a memory and a printbar. The memory contains scan line data representative of said scan lines. The printbar includes a plurality of nozzles and a printbar circuit. The printbar circuit includes an output buffer and a serial data buffer. The serial data buffer is operably connected to receive serially the scan line data such that the serial data buffer includes scan line data corresponding to a first scan line. The output buffer is operably connected to receive the scan line data from the serial data buffer. The printbar circuit is further operable to cause the plurality of nozzles to print on the recording medium in accordance with the scan line data stored in the output buffer.
A second embodiment of the present invention is a method for printing a raster image organized into a plurality of scan lines on a recording medium. The method first includes storing scan line data representative of said scan lines in a memory. The scan line data is provided serially to a serial data buffer such that the serial data buffer includes scan line data corresponding to a first scan line. The scan line data is transferred from the serial data buffer to an output buffer. The method also includes causing a plurality of nozzles to print on the recording medium in accordance with the scan line data stored in the output buffer.
The above discussed features and advantages, as well as others, may be readily ascertained by those of ordinary skill in the art by reference to the following detailed description and accompanying drawings.